IF you can’t wait until the much buzzed-about “Snakes on a Plane” slithers into theaters on Aug. 18, you can get a reptile fix two days earlier – just rent the suspiciously similar-sounding “Snakes on a Train.”

Where “Snakes on a Plane” stars Samuel L. Jackson as a U.S. marshal coping with venom at 20,000 feet, “Snakes on a Train” features the much lower-profile Alby Castro (who?) in a yarn about snakes unleashed by a “Mayan curse” aboard a Los Angeles-bound train from Mexico.

“Snakes on a Train” is the seventh in a series of low-budget, direct-to-video “mockbusters” over the past year designed to ride the coattails of big-budget studio releases like “The War of the Worlds,” “King Kong” and “The Da Vinci Code.”

“I was taking Amtrak last year, and I found an 18-foot man-eating king cobra in my bathroom,” jokes David Latt of The Asylum – the Los Angeles-based production company and video distributor responsible all of these films.

“That, and we expect, just like our friends at New Line” – the distributor of “Snakes on a Plane,” which declined comment – “the film is more than just a title to laugh at, it’s a message to the audience that the movie will have a train, some snakes and a great deal of fun.”

Low-budget knockoffs have been around since the dawn of home video in the early ’80s, when cheaply animated versions were released to coincide with the theatrical re-releases of Disney classics based on public-domain fairy tales.

But, as Latt tells it, The Asylum accidentally stumbled into a lucrative mini-genre when it decided to ride the coattails of Steven Spielberg’s remake of “The War of the Worlds” last year.

Since the book’s copyright had expired in the United States, Latt himself directed a version starring C. Thomas Howell that arrived in video stores a day before the Cruise-Spielberg movie did (overseas it was titled “Invasion”).

“It performed very well for us,” Latt says. “To date it is our highest-grossing production.”

The Asylum, which had been previously been best known for cheap, direct-to-video horror flicks, quickly followed up with “King of the Lost World,” “When a Killer Calls,” “666: The Child,” “The Da Vinci Treasure” and “Pirates of Treasure Island.”

The films, which typically premiere a couple of days before their studio-inspired brethren, feature direct-to-video vets like Howell, Bruce Boxleitner and Lance Hendricksen.

“Our other tie-ins have had mixed results, but overall they have out-performed our other releases,” Latt says. “There’s no question that when it comes to video premiere titles, the American renter is motivated more by recognizable topics than other elements such as star appeal and genre.”

The mockbusters, mostly shot in and around Los Angeles, typically cost about $1 million or less. Latt says The Asylum can take a movie from concept to the video store shelves in as little as four months.

Reliable sales figures are hard to come by for the titles, which do the lion’s share of their business in rentals at big chains like Blockbuster.

“Typically, these things sell under 500,000 copies apiece, which is a fraction of the millions a big studio DVD will sell,” says Susanne Ault of Video Business magazine. “But they tend to be made so cheaply that they can turn a profit.

“And Asylum likely didn’t spend much on advertising because they had so much built-in awareness,” Ault adds. “People might have even bought it out of confusion.”

Clerks at a couple of Manhattan video stores said this was rarely the case.

“I think consumers are a little smarter than that,” says Scott Weinberg of the genre-film Web site Cinematical.

“These are movies that are made for 14-year-old boys that want to rent something with a cool cover. They say, ‘I can’t see ‘The Da Vinci Code’ until next week, so this is a good place holder.”

Weinberg, one of the few reviewers who have bothered with The Asylum oeuvre, thinks “H.G. Wells’ War of the Worlds” is by far the best of the bunch, but “they’re not for film critics. They’re assembly line hack jobs that are fun in fits and starts.”

He notes that most of the movies that The Asylum is tying in with are already remakes or sequels, “so if the studios can cannibalize themselves, who’s to say a young upstart company can’t do the same thing?”

Latt claims he hasn’t had any problems with the big studios, though adds “we did receive a letter from one. We agreed to a small change in the font of our title treatment and that was it.”

Moviemakers have had fairly free reign to make copycat films since 1931, when the U.S. Supreme Court ruled against playwright Anne Nichols, who had claimed Universal Pictures infringed the copyright of “Abie’s Irish Rose,” her famous comedy about mixed marriages, with a series of B movies about “The Cohens and the Kellys.”

Latt says The Asylum is constantly studying the release schedules of studios, which announce dates as far as two years in advance for big movies.

“We look at the buzz and interest level of the audience and the films,” he says. “It’s less about what the studios are interested in and more what interests the worldwide audience.”

So what knockoffs are coming up after “Snakes on a Train”?

“We really can’t say,” Latt says without a hint of irony. “There are too many companies out there who will rip us off.”